<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../vue-2.4.0.js"></script>
</head>
<body>
    <div id='app'>
        <input type="text" v-model:value='value1'>
        <select v-model:value='opration'>
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>
        <input type="text" v-model:value='value2'>
        <button @click='calc'>=</button>
        <input type="text" v-model:value='result'>
    </div>
</body>
<script >
     var vm = new Vue({
            el: '#app',
            data: {
                value1: '',
                value2: '',
                opration: '+',
                result: ''
            },
            methods:{
                calc() {
                    switch (this.opration) {
                        case '+':
                            this.result = Number(this.value1) + Number(this.value2);
                            break;
                        case '-':
                            this.result = Number(this.value1) - Number(this.value2);
                            break;
                        case '*':
                            this.result = Number(this.value1) * Number(this.value2);
                            break;
                        case '/':
                            this.result = Number(this.value1) / Number(this.value2);
                            break;
                    }
                }
            }
        })
</script>
</html>